What is Distilled Water?

by Lucy Bell-Young

Water that has been heated into a vapour and then condensed back to a liquid is known as distilled water. It is a form of purified water that has had all of its impurities removed, and for this reason, is used in a variety of industrial applications.

About Distilled Water

Distilled water is not a modern-day phenomenon but a benchmark of civilisation. The earliest recording of this substance is dated back to c. 384 – 322 B.C. in Aristotle’s Meteorologica, where the philosopher discusses how seawater can be evaporated to produce drinking water. This was distillation at its simplest.

Distilled water is water that has had almost all of its impurities removed. There are many different forms of purified water, including deionised water and demineralised water, which are purified using different treatment methods that remove ionic and mineral impurities, like calcium (Ca+), magnesium (Mg+), nitrate (NO3-) or carbonate (CO32-).

However, distilled water is generally considered to be the purest because it removes organic impurities as well as ions and minerals. This is why it is favoured by industries that require very high-purity conditions, like pharmaceutical manufacturing or automotive companies.

Sea foam on the surface of the ocean
The Ancient Greeks were already practising distillation in 350 B.C. Aristotle wrote about this, saying how sea water can be evaporated to create drinking water.

How is it Made?

Distilled water is made through a process of distillation. Put simply, this involves heating raw water in a distilling flask or container until it begins to vaporise. Since most impurities have a higher boiling point than water, they will not vaporise with the water.

This is how the separation happens. As the water vapour collects at the top of the flask or in its own receiving container, the impurities stay behind in the liquid.

Once the vapours are collected, they are condensed back into a liquid which is called distilled water. When exceptionally high purity water is required, this water sample is put back through the process again. This is called double distillation and it is used to ensure that the final product is as pure as possible.

What Makes Distillation Effective?

Distillation is more effective than other modes of purification, like deionisation or demineralisation. These methods involve passing raw water through ion exchange resins which replace impurity ions with H+ and OH- ions. These then combine to form pure H2O.

While ion exchange is an effective way to purify water, it is unable to remove organic impurities, like bacteria, since these do not have a charge. Distillation, on the other hand, is able to remove organic impurities as well as ions and minerals.

Uses of Distilled Water

Its impeccable purity makes distilled water suitable for a range of industrial applications. This is because it won’t corrode sensitive materials, leave a residue behind or react and interfere with other chemicals. In general, its uses are very similar to the uses of deionised and demineralised water.

  1. Pharmaceuticals

In pharmaceutical manufacturing, it is important that high purity water is used because contaminants in tap water could interfere with other ingredients and cause a chemical reaction. In this industry, distilled water is used in products like:

  • Analytical reagents
  • Active pharmaceutical ingredients
  • Active pharmaceutical intermediates

It is also used in cosmetic products like creams or shower products. Demineralised water is sometimes used in pharmaceuticals because it is cheaper than distilled water. However, if the product or process requires very high purity, distilled water is generally preferred.

A pile of pills with a pipette on top
Distilled water is used in the pharmaceutical industry in a variety of product formulations, including analytical reagents and APIs.
  1. Medical Procedures

In the medical world, the water used has to meet a very exact specification in order to be suitable for use. Very high-purity distilled water is often used in this industry to carry out a range of medical procedures:

  • Cleaning wounds because it helps to avoid the tissue getting infected
  • Irrigation solutions during surgery because prevents bacteria from entering the body cavity
  • Mouth rinsing in dentistry to prevent infection of the open wound after something like a tooth extraction
  • CPAP (Constant Positive Airway Pressure) machines because it can humidify the air for breathing and won’t leave behind any contaminants

If you’ve ever scraped your knee and had to receive first aid, it is usually distilled water that is used to clean the wound. This because it prevents any bacteria from spreading.

  1. Laboratory Applications

Purified water in the laboratory is critical in creating controlled environments and in obtaining high-quality products. Distilled water is used in the lab:

  • As a solvent to prepare solutions and buffers
  • In autoclaves to extend the life of the chamber
  • To clean glassware and other sensitive equipment

In the lab, the type of water used is crucial to the integrity of precise data, analyses and final products. This because water impurities can easily render an experiment useless, interfere with results and contaminate chemical formulations.

  1. Automotive and Metal Parts

The type of water you use on your car engine or lead-acid battery is very important. If you use tap water, for example, its high calcium content will build-up on the surface over time and eventually corrode the metal parts.

The lack of impurities in distilled water makes it ideally suited for use in:

  • Lead-acid batteries
  • Cooling systems
  • Aircraft engines
  • Gas-turbine engines

Distilled water can also be safely used on different metal parts, including the boiler system in steam engines or to simply clean metal equipment.

Back end of a car in traffic
Distilled water is commonly used in the automotive industry because it won’t corrode the metal parts.
  1. Other Uses

Like most purified water products, there a huge range of applications that distilled water gets involved in. These include, but are not limited to:

  • In the electronic industry to wash down circuit boards
  • In low-volume humidifiers like cigar humidors to avoid mineral deposits
  • In early airplanes like the Boeing 707 to increase the density of air during take-off

Can You Drink Distilled Water?

The word ‘impurities’ may sound like something you don’t want in your body, but when it comes to water they shouldn’t be avoided. This is because impurity minerals found in drinking water, especially ones like calcium, play a crucial role in our diet.

While drinking a glass of distilled water isn’t going to hurt you, if you continue to drink it over time you will be depriving your body of these essential minerals and ions. This is why distilled water often tastes strange and leaves a furry texture on your tongue.

It may even be capable of removing existing minerals and electrolytes from your body. So while drinking distilled water isn’t like drinking a cup of poison, it isn’t recommended.

Droplets of water vapour on a window. This is how distilled water is produced.

ReAgent not only has a huge range of purified water products, we also have a brand new water treatment plant that ensures our distilled water is as pure as possible. We are internationally recognised for our outstanding quality and even offer free technical advice should you need it.


The blog on chemicals.co.uk and everything published on it is provided as an information resource only. The blog, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website. We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label. If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).